Advanced copper interconnects with hybrid microstructure

ABSTRACT

A device relates to a semiconductor device. The semiconductor device includes a narrow-line bamboo microstructure integrated within a metal layer of the semiconductor device and a narrow-line polycrystalline microstructure. The narrow-line polycrystalline microstructure is integrated within the same metal layer as the narrow-line bamboo microstructure.

BACKGROUND

The present invention relates to semiconductor devices, and morespecifically, to the presence of a narrow-line bamboo microstructure andnarrow-line polycrystalline microstructure integrated in the same metallayer.

Generally, semiconductor devices include a plurality of circuits whichform an integrated circuit fabricated on a semiconductor substrate. Acomplex network of signal paths will normally be routed to connect thecircuit elements distributed on the surface of the substrate. Efficientrouting of these signals across the device requires formation ofmultilevel or multilayered schemes, such as, for example, single or dualdamascene wiring structures. The wiring structure typically includescopper, Cu.

SUMMARY

According to one embodiment, a method of forming a semiconductor deviceis provided. The method includes applying a masking material to a firstportion of a dielectric layer; forming a first masked portion of thedielectric layer; forming a first narrow-line trench in a second portionof the dielectric layer, wherein the first narrow-line trench has adepth, d₁; forming a second narrow-line trench in the first portion ofthe dielectric layer, wherein the second narrow-line trench has a depth,d₂, wherein the depth d₁ is smaller than the depth d₂; depositing aliner material into the first narrow-line trench and the secondnarrow-line trench and onto the dielectric layer; plating copper ontothe liner material; and annealing the dielectric layer to form thesemiconductor device, wherein a narrow-line bamboo microstructure isformed in the second portion of the dielectric layer and wherein anarrow-line polycrystalline microstructure is formed in the firstportion of the dielectric layer.

According to one embodiment, a semiconductor device is provided. Thesemiconductor device includes a narrow-line bamboo microstructureintegrated within a metal layer of the semiconductor device; and anarrow-line polycrystalline microstructure; wherein the narrow-linepolycrystalline microstructure is integrated within the same metal layeras the narrow-line bamboo microstructure.

According to one embodiment, an integrated circuit is provided. Theintegrated circuit includes a narrow-line bamboo microstructureintegrated within a metal layer of the semiconductor device, wherein thenarrow-line bamboo microstructure comprises nanowires configured toprovide a high reliability resistance circuit and wherein thenarrow-line bamboo microstructure has a depth, d₁; and a narrow-linepolycrystalline microstructure wherein the narrow-line polycrystallinemicrostructure has a higher depth in the metal layer as compared to thenarrow-line bamboo microstructure and wherein the narrow-linepolycrystalline microstructure has a depth, d₂, wherein d₁ is less thand₂; wherein the narrow-line polycrystalline microstructure is integratedwithin the same metal layer as the narrow-line bamboo microstructure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional illustration of metal layer of asemiconductor device having a narrow-line polycrystalline microstructureand a narrow-line bamboo microstructure according to an embodiment.Narrow-line as described herein generally refers to a minimum width on afeature side of the microstructure. The minimum width can be less thanor equal to 175 nanometers (nm), for example, less than or equal to 100nm, for example, less than or equal to 75 nm.

FIG. 2 is a cross-sectional view a semiconductor device illustratingblocking of one portion of a metal layer to form a narrow-line bamboomicrostructure on the other portion of the metal layer according to anembodiment.

FIG. 3 is a cross-sectional view of a semiconductor device illustratingblocking of the portion of the metal layer on which the bamboo structureis located in order to form a polycrystalline structure on anotherportion of the metal layer according to an embodiment.

FIG. 4 is a cross-sectional view of the semiconductor device afterdeposition of liner material and copper filling according to anembodiment.

FIG. 5 is a cross-sectional view of the semiconductor device afterthermal annealing according to an embodiment.

DETAILED DESCRIPTION

Within a typical interconnect structure, metal vias run perpendicular tothe semiconductor substrate and metal lines run parallel to thesemiconductor substrate. Further enhancement of the signal speed andreduction of signals in adjacent metal lines (known as “crosstalk”) areachieved in integrated circuit product chips by embedding the metallines and metal vias (e.g., conductive features) in a dielectricmaterial having a dielectric constant of less than silicon dioxide.

Conductive material within the conductive region has a lowelectromigration resistance due to a high number of electromigrationpaths inside the conductive region. The electromigration problem isexpected to increase in future semiconductor technologies due to thescaling of such devices.

Thus, there is a continued desire to provide interconnect structureswhere the electromigration has been substantially reduced and/oreliminated.

Copper diffusion in semiconductor devices can occur through copper grainboundaries, increasingly so when narrow-line polycrystallinemicrostructure s are present. To provide increased electromigrationresistance (e.g., greater than 0.9 electron Volt (eV) ofelectromigration activation energy), it can be desirable to providecopper wires (i.e., interconnects) with narrow-line bamboomicrostructures. Since narrow-line bamboo microstructures dispersedwithin shallow features provide lower conductivity than narrow-linepolycrystalline microstructure s, it can be desirable to include bothnarrow-line polycrystalline microstructure s and narrow-line bamboomicrostructures within the same metal layer of a semiconductor device.Such a semiconductor device can provide the desired qualities of highconductivity (e.g., less than 4 microOhm-centimeters (μΩ—cm) copper (Cu)resistivity in lines having a thickness of less than 100 nm) and highelectromigration resistance.

FIG. 1 is a longitudinal illustration of a metal layer 100 of asemiconductor device. The metal layer 100 includes a low-κ dielectricmaterial 102 with a liner material 104 disposed adjacent to the low-κdielectric material 104 with copper 106 disposed adjacent to the linermaterial 104 such that the liner material 104 is located between thelow-κ dielectric material 102 and the copper 106. Narrow-line bamboomicrostructure 110 and narrow-line polycrystalline microstructure 108are both present in metal layer 100. In the narrow-line bamboomicrostructure 110, the grain boundaries can end at either a top of thesurface of the copper 106 or at an interface between the copper 106 andliner material 104. With the narrow-line bamboo microstructure 110,there are not triple junctions as can be observed in the narrow-linepolycrystalline microstructure. The narrow-line bamboo microstructure110 and the narrow-line polycrystalline microstructure can each includenanowires. In the narrow-line bamboo microstructure 110, grainboundaries can be perpendicular to a width of the wire and to currentflow. As a result, boundary diffusion can be reduced or eliminated alsothereby reducing or eliminating material transport. As illustrated inFIG. 1, narrow-line bamboo microstructure 110 can be substantiallyperpendicular to liner material 104. It is to be understood, however,the narrow-line bamboo microstructure does not have to be perpendicularto the liner material 104.

An interconnect structure can be made by utilizing interconnectprocessing, e.g., by applying the dielectric material 102 to a surfaceof a substrate (not shown). The substrate, which is not shown, cancomprise a semiconducting material, an insulating material, a conductivematerial or a combination comprising at least one of the foregoing. Whenthe substrate is comprised of a semiconducting material, anysemiconductor such as Si, SiGe, SiGeC, SiC, Ge alloys, GaAs, InAs, InPand other III/V or II/VI compound semiconductors may be used. Inaddition to these listed types of semiconducting materials, thesemiconductor substrate can be a layered semiconductor such as, forexample, Si/SiGe, Si/SiC, silicon-on-insulators (SOIs) or silicongermanium-on-insulators (SGOIs).

When the substrate is an insulating material, the insulating materialcan be an organic insulator, an inorganic insulator or a combinationcomprising at least one of the foregoing including multilayers. When thesubstrate is a conducting material, the substrate can include, forexample, polySi, an elemental metal, alloys of elemental metals, a metalsilicide, a metal nitride or a combination comprising at least one ofthe foregoing including multilayers. When the substrate comprises asemiconducting material, one or more semiconductor devices such as, forexample, complementary metal oxide semiconductor (CMOS) devices can befabricated thereon.

The low-κ dielectric material 102 can include any interlevel orintralevel dielectric including inorganic dielectrics or organicdielectrics. The low-κ dielectric material 102 can be porous ornon-porous. Some examples of dielectrics that can be used as the low-κdielectric material 102 include, but are not limited to: SiO2,silsesquixoanes, C doped oxides (i.e., organosilicates) that includeatoms of Si, C, O and H, thermosetting polyarylene ethers, ormultilayers thereof. The term “polyarylene” is used in this applicationto denote aryl moieties or inertly substituted aryl moieties which arelinked together by bonds, fused rings, or inert linking groups such as,for example, oxygen, sulfur, sulfone, sulfoxide, carbonyl and the like.

The low-κ dielectric material 102 can have a dielectric constant that isabout 3.0 or less, with a dielectric constant of about 2.8 or less beingeven more typical. These dielectrics generally have a lower parasiticcross talk as compared with dielectric materials that have a higherdielectric constant than 3.0. The thickness of the low-κ dielectricmaterial 102 can vary depending upon the dielectric material used aswell as the exact number of dielectrics metal layer 12. For example, thelow-κ dielectric material 102 can have a thickness from about 200 toabout 450 nm.

The portion of the metal layer 100 with the narrow-line bamboomicrostructure 110 can provide high reliability, e.g., highelectromigration resistance, while the portion of the metal layer 100with the narrow-line polycrystalline microstructure 108 can provide highperformance, e.g., high conductivity. For example, the narrow-linebamboo microstructure 110 can be configured to provide a highreliability resistance circuit such as high electromagnetic resistanceas compared to the polycrystalline structure 108. The narrow-linepolycrystalline microstructure 108 can be configured to provide a highperformance circuit, such as higher conductivity as compared to thenarrow-line bamboo microstructure 110.

As illustrated in FIG. 1, the narrow-line polycrystalline microstructure108 can have a higher (i.e., longer) depth in the metal layer 100 ascompared to the narrow-line bamboo microstructure 110. For example,compared to the narrow-line bamboo microstructure 110, thepolycrystalline area has a larger copper cross-sectional area and canprovide a higher conductivity due to the larger cross-sectional area.

FIGS. 2 and 3 illustrate the blocking portion of the process in forminga metal layer 100 with a narrow-line bamboo microstructure 110 and anarrow-line polycrystalline microstructure 108. As can be seen in FIGS.2 and 3, a method of forming a semiconductor device can include applyinga masking material 112 to a first portion 114 of a dielectric layer 102forming a first masked portion. A trench 118 can be formed in a secondportion 116 of the dielectric layer 102. The trench 118 can have adepth, d₁. Masking material 122 can be applied to the first portion 114of the dielectric layer 102 during formation of trenches 118 and to thesecond portion 116 of the dielectric layer 102 during formation oftrenches 120. The masking material 112 can include insulators, e.g.,silicon nitride (SiN) or metallic materials, e.g., tantalum nitride(TaN), titanium nitride (TiN), or a combination comprising at least oneof the foregoing. The masking material 112 can include organic anorganic photoresist material, A masking material 112 can be applied tothe second portion 116 of the dielectric layer 102. A trench 120 can beformed in the first portion 114 of the dielectric layer 102. The trench120 can have a depth, d₂. Depth, d₁ can have a smaller value than thedepth, d₂. The trenches 118, 120 can have be narrow-line trenches, i.e.,the trenches 118, 120 can have a minimum width on a feature side of lessthan or equal to 175 nm, for example, less than or equal to 100 nm, forexample, less than or equal to 75 nm.

Turning now to FIGS. 4 and 5, a liner material 124 can be deposited intothe first trench 118 and the second trench 120 and onto the dielectriclayer 102. The liner material can include tantalum, titanium, tungsten,cobalt, ruthenium, nitrides thereof, or a combination comprising atleast one of the foregoing. Copper (Cu) 126 can be plated onto the linermaterial 124. Following the copper plating process illustrated in FIG.4, there is no obvious microstructure differences between first portion114 and second portion 116. Both first portion 114 and second portion116 contain narrow-line polycrystalline microstructures. Copper 126 canbe annealed at a temperature of 100 to 400 ° C. for 0.5 to 4 hours toform the semiconductor device. During the annealing process, Curecrystallization and grain growth start to modulate the interconnectmicrostructure in order to reduce the overall energy. Cu grain growth isnormally observed from the top Cu overburden area and grows into thepatterned and smaller dimensional features. The driving force isnormally sufficient to prompt the grain growth into a top portion of thepatterned features, but not enough to completely penetrate into a bottomof a deep feature. A narrow-line bamboo microstructure 110 is formed inthe second portion 116 of the copper 126 after annealing as illustratedin FIG. 5 and a narrow-line polycrystalline microstructure 108 is formedin the first portion 114 of copper 126 after annealing.

Although illustrated with respect to one metal layer in a semiconductordevice, the narrow-line bamboo microstructure 110 and the narrow-linepolycrystalline microstructure 108 can be located in more than one layerin the semiconductor device (e.g., greater than or equal to 1 layer). Anaspect ratio between (e.g., height to width) the narrow-line bamboomicrostructure 110 and the narrow-line polycrystalline microstructure108 can be greater than 0.5. The metal layer 100 can be subjected to apolishing process such as chemical mechanical planarization (CMP) afterformation of the narrow-line bamboo microstructure 110 and thenarrow-line polycrystalline microstructure 108.

An integrated circuit can be formed using the semiconductor devicedisclosed herein.

Deposition is any process that grows, coats, or otherwise transfers amaterial onto the wafer. Available technologies include, but are notlimited to, thermal oxidation, physical vapor deposition (PVD), chemicalvapor deposition (CVD), electrochemical deposition (ECD), molecular beamepitaxy (MBE) and more recently, atomic layer deposition (ALD) amongothers.

Removal is any process that removes material from the wafer: examplesinclude etch processes (either wet or dry), and chemical-mechanicalplanarization (CMP), etc.

Patterning is the shaping or altering of deposited materials, and isgenerally referred to as lithography. For example, in conventionallithography, the wafer is coated with a chemical called a photoresist;then, a machine called a stepper focuses, aligns, and moves a mask,exposing select portions of the wafer below to short wavelength light;the exposed regions are washed away by a developer solution. Afteretching or other processing, the remaining photoresist is removed.Patterning also includes electron-beam lithography, nanoimprintlithography, and reactive ion etching.

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

As used herein, the articles “a” and “an” preceding an element orcomponent are intended to be nonrestrictive regarding the number ofinstances (i.e. occurrences) of the element or component. Therefore, “a”or “an” should be read to include one or at least one, and the singularword form of the element or component also includes the plural unlessthe number is obviously meant to be singular.

As used herein, the terms “invention” or “present invention” arenon-limiting terms and not intended to refer to any single aspect of theparticular invention but encompass all possible aspects as described inthe specification and the claims.

As used herein, the term “about” modifying the quantity of aningredient, component, or reactant of the invention employed refers tovariation in the numerical quantity that can occur, for example, throughtypical measuring and liquid handling procedures used for makingconcentrates or solutions. Furthermore, variation can occur frominadvertent error in measuring procedures, differences in themanufacture, source, or purity of the ingredients employed to make thecompositions or carry out the methods, and the like. In one aspect, theterm “about” means within 10% of the reported numerical value. Inanother aspect, the term “about” means within 5% of the reportednumerical value. Yet, in another aspect, the term “about” means within10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% of the reported numerical value.

In the foregoing description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide a thoroughunderstanding of the present invention. However, it will be appreciatedby one of ordinary skill in the art that the present disclosure may bepracticed with viable alternative process options without these specificdetails. In other instances, well-known structures or processing stepshave not been described in detail in order to avoid obscuring thevarious embodiments of the present disclosure.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

1. A method of forming a semiconductor device, comprising: applying amasking material to a first portion of a dielectric layer; forming afirst masked portion of the dielectric layer; forming a firstnarrow-line trench in a second portion of the dielectric layer, whereinthe first narrow-line trench has a depth, d₁; forming a secondnarrow-line trench in the first portion of the dielectric layer, whereinthe second narrow-line trench has a depth, d₂, wherein the depth d₁ issmaller than the depth d₂; depositing a liner material into the firstnarrow-line trench and the second narrow-line trench and onto thedielectric layer; plating copper onto the liner material; and annealingthe dielectric layer to form the semiconductor device, wherein anarrow-line bamboo microstructure is formed in the second portion of thedielectric layer and wherein a narrow-line polycrystallinemicrostructure is formed in the first portion of the dielectric layer.2. The method of claim 1, wherein the liner material comprises tantalum,titanium, tungsten, cobalt, ruthenium, and their nitrides thereof, or acombination comprising at least one of the foregoing.
 3. The method ofclaim 1, further comprising applying a masking material to the secondportion of the dielectric layer before forming the second narrow-linetrench.
 4. The method of claim 1, wherein the annealing is done at atemperature of 100 to 400° C. for 0.5 to 4 hours.
 5. The method of claim1, further comprising polishing the semiconductor device with chemicalmechanical planarization.
 6. The method of claim 1, wherein thedielectric layer comprises a low-κ dielectric material.
 7. The method ofclaim 6, wherein the dielectric layer comprises silicon dioxide.
 8. Themethod of claim 1, wherein the narrow-line bamboo microstructurecomprises nanowires configured to provide a high reliability resistancecircuit.
 9. The method of claim 8, wherein the narrow-line bamboomicrostructure has high electromagnetic resistance as compared to thepolycrystalline structure.
 10. The method of claim 1, wherein thenarrow-line polycrystalline microstructure has higher conductivity ascompared to the narrow-line bamboo microstructure. 11.-20. (canceled)21. The method of claim 1, wherein the narrow-line bamboo microstructureand the narrow-line polycrystalline microstructure comprise copperinterconnects.
 22. The method of claim 1, wherein the narrow-linepolycrystalline microstructure comprises nanowires configured to providea high performance circuit.
 23. The method of claim 1, wherein thenarrow-line polycrystalline microstructure has a higher depth in themetal layer as compared to the narrow-line bamboo microstructure. 24.The method of claim 1, wherein a difference in aspect ratio between thenarrow-line bamboo microstructure and the narrow-line polycrystallinemicrostructure is greater than 0.5.
 25. The method of claim 1, whereinthe narrow-line bamboo microstructure is dispersed in greater than orequal to 1 layer of the semiconductor device and/or wherein thenarrow-line polycrystalline microstructure is dispersed in greater thanor equal to 1 layer of the semiconductor device.
 26. The method of claim1, wherein the narrow-line polycrystalline microstructure is integratedwithin the same metal layer as the narrow-line bamboo microstructure.